Resin composition for forming a phase-separated structure, and method of producing structure containing phase-separated structure

ABSTRACT

A resin composition for forming a phase-separated structure, including: a block copolymer, and an ion liquid containing a compound (IL) having a cation moiety and an anion moiety, the energy of the LUMO of the cation moiety being −4.5 eV or more, and the energy difference between the LUMO and the HOMO of the cation moiety being 10.0 ev or more, or the Log P value of the anion moiety being 1 to 3.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under grant number1344891 awarded by National Science Foundation. The government hascertain rights in the invention.

TECHNICAL FIELD

The present invention relates to a resin composition for forming aphase-separated structure, and a method of producing a structurecontaining a phase-separated structure.

DESCRIPTION OF RELATED ART

Recently, as further miniaturization of large scale integrated circuits(LSI) proceeds, a technology for processing a more delicate structure isdemanded.

In response to such demand, development has been conducted on atechnology in which a fine pattern is formed using a phase-separatedstructure formed by self-assembly of a block copolymer having mutuallyincompatible blocks bonded together (see, for example, Patent Document1).

For using a phase-separation structure of a block copolymer, it isnecessary to form a self-organized nano structure by a microphaseseparation only in specific regions, and arrange the nano structure in adesired direction. For realizing position control and orientationalcontrol, processes such as graphoepitaxy to control phase-separatedpattern by a guide pattern and chemical epitaxy to controlphase-separated pattern by difference in the chemical state of thesubstrate are proposed (see, for example, Non-Patent Document 1).

A block copolymer forms a regular periodic structure by phaseseparation.

A “period of a structure” refers to a period of a phase structureobserved when a phase-separated structure is formed, and is a sum of thelengths of the phases which are mutually incompatible. In the case offorming a cylinder structure which has a phase-separated structureperpendicular to a surface of a substrate, the period (L0) of thestructure is the center distance (pitch) of two mutually adjacentcylinder structures.

It is known that the period (L0) of a block polymer is determined byintrinsic polymerization properties such as the polymerization degree Nand the Flory-Huggins interaction parameter χ. Specifically, therepulsive interaction between different block components of the blockcopolymer becomes larger as the product of χ and N, “χ·N” becomeslarger. Therefore, when χ·N>10 (hereafter, referred to as “strongsegregation limit”), there is a strong tendency for the phase separationto occur between different blocks in the block copolymer. At the strongsegregation limit, the period of the block copolymer is approximatelyN^(2/3)·χ^(1/6), and a relationship represented by following formula (1)is satisfied. That is, the period of the structure is in proportion tothe polymerization degree N which correlates with the molecular weightand molecular weight ratio between different blocks.L0∝a·N ^(2/3)·χ^(1/6)  (1)

In the formula, L0 represents the period of the structure; a representsa parameter indicating the size of the monomer; N represents thepolymerization degree; and χ indicates an interaction parameter. Thelarger the value of the interaction parameter, the higher thephase-separation performance.

Therefore, by adjusting the composition and the total molecular weightof the block copolymer, the period (L0) of the structure can beadjusted.

It is known that the periodic structure formed by a block copolymerchanges to a cylinder, a lamellar or a sphere, depending on the volumeratio or the like of the polymer components. Further, it is known thatthe period depends on the molecular weight.

Therefore, in order to form a structure having a relatively large period(L0) using a phase-separated structure formed by self-assembly of ablock copolymer, it is considered that such structure may be formed byincreasing the molecular weight of the block copolymer.

DOCUMENTS OF RELATED ART Patent Literature

-   [Patent Document 1] Japanese Unexamined Patent Application, First    Publication No. 2008-36491

Non-Patent Documents

-   [Non-Patent Document 1] Proceedings of SPIE (U.S.), vol. 7637, pp.    76370G-1 (2010)

SUMMARY OF THE INVENTION

However, currently, in the case of forming a structure using aphase-separated structure formed by directed self-assembly of a widelyused block copolymer (e.g., a block copolymer having a styrene block anda methyl methacrylate block), is was difficult to further improve thephase-separation performance.

The present invention takes the above circumstances into consideration,with an object of providing a resin composition for forming aphase-separated structure with improved phase-separation performance.

For solving the above-mentioned problems, the present invention employsthe following aspects.

A first aspect of the present invention is a resin composition forforming a phase-separated structure, including: a block copolymer, andan ion liquid containing a compound (IL) having a cation moiety and ananion moiety, the energy of the LUMO of the cation moiety being −4.5 eVor more, and the energy difference between the LUMO and the HOMO of thecation moiety being 10.0 ev or more, or the Log P value of the anionmoiety being 1 to 3.

A second aspect of the present invention is a method of producing astructure containing a phase-separated structure, including: using theresin composition for forming a phase-separated structure according tothe first aspect to form a layer containing a block copolymer, andphase-separating the layer containing the block copolymer.

According to the present invention, there is provided a resincomposition for forming a phase-separated structure with improvedphase-separation performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example of one embodiment ofthe method of forming a structure containing a phase-separated structureaccording to a second aspect of the present invention.

FIG. 2 is an explanatory diagram showing an example of one embodiment ofan optional step.

DETAILED DESCRIPTION OF THE INVENTION

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

The term “alkylene group” includes linear, branched or cyclic, divalentsaturated hydrocarbon, unless otherwise specified.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a groupin which part or all of the hydrogen atoms of an alkyl group or analkylene group have been substituted with a fluorine atom.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (resin, polymer, copolymer).

The expression “may have a substituent” means that a case where ahydrogen atom (—H) is substituted with a monovalent group, or a casewhere a methylene (—CH₂—) group is substituted with a divalent group.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

A “structural unit derived from an acrylate ester” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of an acrylate ester.

An “acrylate ester” refers to a compound in which the terminal hydrogenatom of the carboxy group of acrylic acid (CH₂═CH—COOH) has beensubstituted with an organic group.

The acrylate ester may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent. The substituent(R^(α0)) that substitutes the hydrogen atom bonded to the carbon atom onthe α-position is an atom other than hydrogen or a group, and examplesthereof include an alkyl group of 1 to 5 carbon atoms and a halogenatedalkyl group of 1 to 5 carbon atoms. Further, an acrylate ester havingthe hydrogen atom bonded to the carbon atom on the α-positionsubstituted with a substituent (R^(α0)) in which the substituent hasbeen substituted with a substituent containing an ester bond (e.g., anitaconic acid diester), or an acrylic acid having the hydrogen atombonded to the carbon atom on the α-position substituted with asubstituent (R^(α0)) in which the substituent has been substituted witha hydroxyalkyl group or a group in which the hydroxy group within ahydroxyalkyl group has been modified (e.g., α-hydroxyalkyl acrylateester) can be mentioned as an acrylate ester having the hydrogen atombonded to the carbon atom on the α-position substituted with asubstituent. A carbon atom on the α-position of an acrylate ester refersto the carbon atom bonded to the carbonyl group, unless specifiedotherwise.

Hereafter, an acrylate ester having the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent issometimes referred to as “α-substituted acrylate ester”. Further,acrylate esters and α-substituted acrylate esters are collectivelyreferred to as “(α-substituted) acrylate ester”.

A “structural unit derived from hydroxystyrene” refers to a structuralunit that is formed by the cleavage of the ethylenic double bond ofhydroxystyrene. A “structural unit derived from a hydroxystyrenederivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of a hydroxystyrene derivative.

The term “hydroxystyrene derivative” includes compounds in which thehydrogen atom at the α-position of hydroxystyrene has been substitutedwith another substituent such as an alkyl group or a halogenated alkylgroup; and derivatives thereof. Examples of the derivatives thereofinclude hydroxystyrene in which the hydrogen atom of the hydroxy grouphas been substituted with an organic group and may have the hydrogenatom on the α-position substituted with a substituent; andhydroxystyrene which has a substituent other than a hydroxy group bondedto the benzene ring and may have the hydrogen atom on the α-positionsubstituted with a substituent. Here, the α-position (carbon atom on theα-position) refers to the carbon atom having the benzene ring bondedthereto, unless specified otherwise.

As the substituent which substitutes the hydrogen atom on the α-positionof hydroxystyrene, the same substituents as those described above forthe substituent on the α-position of the aforementioned α-substitutedacrylate ester can be mentioned.

The term “styrene” is a concept including styrene and compounds in whichthe hydrogen atom at the α-position of styrene is substituted with othersubstituent such as an alkyl group and a halogenated alkyl group.

The term “styrene derivative” includes compounds in which the hydrogenatom at the α-position of styrene has been substituted with anothersubstituent such as an alkyl group or a halogenated alkyl group; andderivatives thereof. Examples of the derivatives thereof includehydroxystyrene which has a substituent other than a hydroxy group bondedto the benzene ring and may have the hydrogen atom on the α-positionsubstituted with a substituent. Here, the α-position (carbon atom on theα-position) refers to the carbon atom having the benzene ring bondedthereto, unless specified otherwise.

A “structural unit derived from styrene” or “structural unit derivedfrom a styrene derivative” refers to a structural unit that is formed bythe cleavage of the ethylenic double bond of styrene or a styrenederivative.

As the alkyl group as a substituent on the α-position, a linear orbranched alkyl group is preferable, and specific examples include alkylgroups of 1 to 5 carbon atoms, such as a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Specific examples of the halogenated alkyl group as the substituent onthe α-position include groups in which part or all of the hydrogen atomsof the aforementioned “alkyl group as the substituent on the α-position”are substituted with halogen atoms. Examples of the halogen atom includea fluorine atom, a chlorine atom, a bromine atom and an iodine atom, anda fluorine atom is particularly desirable.

Specific examples of the hydroxyalkyl group as the substituent on theα-position include groups in which part or all of the hydrogen atoms ofthe aforementioned “alkyl group as the substituent on the α-position”are substituted with a hydroxy group. The number of hydroxy groupswithin the hydroxyalkyl group is preferably 1 to 5, and most preferably1.

(Resin Composition for Forming Phase-Separated Structure)

The resin composition for forming a phase-separated structure accordingto a first aspect of the present invention (hereafter, referred tosimply as “resin composition”) includes a block copolymer, and an ionliquid containing a compound (IL) having a cation moiety and an anionmoiety.

As one embodiment of the resin composition, for example, a blockcopolymer and the ion liquid may be dissolved in an organic solventcomponent.

<Block Copolymer>

A block copolymer is a polymeric material in which plurality of blocks(partial constitutional components in which the same kind of structuralunit is repeatedly bonded) are bonded. As the blocks constituting theblock copolymer, 2 kinds of blocks may be used, or 3 or more kinds ofblocks may be used.

The plurality of blocks constituting the block copolymer are notparticularly limited, as long as they are combinations capable ofcausing phase separation. However, it is preferable to use a combinationof blocks which are mutually incompatible. Further, it is preferable touse a combination in which a phase of at least one block amongst theplurality of blocks constituting the block copolymer can be easilysubjected to selective removal as compared to the phases of otherblocks.

Further, it is preferable to use a combination in which a phase of atleast one block amongst the plurality of blocks constituting the blockcopolymer can be easily subjected to selective removal as compared tothe phases of other blocks. An example of a combination which can beselectively removed reliably include a block copolymer in which one ormore blocks having an etching selectivity of more than 1 are bonded.

Examples of the block copolymer include a block copolymer in which ablock of a structural unit having an aromatic group is bonded to a blockof a structural unit derived from an (α-substituted) acrylate ester; ablock copolymer in which a block of a structural unit having an aromaticgroup is bonded to a block of a structural unit derived from an(α-substituted) acrylic acid; a block copolymer in which a block of astructural unit having an aromatic group is bonded to a block of astructural unit derived from siloxane or a derivative thereof; a blockcopolymer in which a block of a structural unit derived from analkyleneoxide is bonded to a block of a structural unit derived from an(α-substituted) acrylate ester; a block copolymer in which a block of astructural unit derived from an alkyleneoxide is bonded to a block of astructural unit derived from an (α-substituted) acrylic acid; a blockcopolymer in which a block of a structural unit containing a polyhedraloligomeric silsesquioxane structure is bonded to a block of a structuralunit derived from an (α-substituted) acrylate ester; a block copolymerin which a block of a structural unit containing a silsesquioxanestructure is bonded to a block of a structural unit derived from an(α-substituted) acrylic acid; and a block copolymer in which a block ofa structural unit containing a silsesquioxane structure is bonded to ablock of a structural unit derived from siloxane or a derivativethereof.

Examples of the structural unit having an aromatic group includestructural units having a phenyl group, a naphthyl group or the like.Among these examples, a structural unit derived from styrene or aderivative thereof is preferable.

Examples of the styrene or derivative thereof include α-methylstyrene,2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-t-butylstyrene,4-n-octylstyrene, 2,4,6-trimethylstyrene, 4-methoxystyrene,4-t-butoxystyrene, 4-hydroxystyrene, 4-nitrostyrene, 3-nitrostyrene,4-chlorostyrene, 4-fluorostyrene, 4-acetoxyvinylstyrene,4-vinylbenzylchloride, 1-vinylnaphthalene, 4-vinylbiphenyl,1-vinyl-2-pyrolidone, 9-vinylanthracene, and vinylpyridine.

An (α-substituted) acrylic acid refers to either or both acrylic acidand a compound in which the hydrogen atom bonded to the carbon atom onthe α-position of acrylic acid has been substituted with a substituent.As an example of such a substituent, an alkyl group of 1 to 5 carbonatoms can be given.

Examples of (α-substituted) acrylic acid include acrylic acid andmethacrylic acid.

An (α-substituted) acrylate ester refers to either or both acrylateester and a compound in which the hydrogen atom bonded to the carbonatom on the α-position of acrylate ester has been substituted with asubstituent. As an example of such a substituent, an alkyl group of 1 to5 carbon atoms can be given.

Specific examples of the (α-substituted) acrylate ester include acrylateesters such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butylacrylate, t-butyl acrylate, cyclohexyl acrylate, octyl acrylate, nonylacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, benzylacrylate, anthracene acrylate, glycidyl acrylate,3,4-epoxycyclohexylmethane acrylate, and propyltrimethoxysilaneacrylate; and methacrylate esters such as methyl methacrylate, ethylmethacrylate, propyl methacrylate, n-butyl methacrylate, t-butylmethacrylate, cyclohexyl methacrylate, octyl methacrylate, nonylmethacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate,benzyl methacrylate, anthracene methacrylate, glycidyl methacrylate,3,4-epoxycyclohexylmethane methacrylate, and propyltrimethoxysilanemethacrylate.

Among these, methyl acrylate, ethyl acrylate, t-butyl acrylate, methylmethacrylate, ethyl methacrylate, and t-butyl methacrylate arepreferable.

Examples of siloxane and siloxane derivatives include dimethylsiloxane,diethylsiloxane, diphenylsiloxane, and methylphenylsiloxane.

Examples of the alkylene oxide include ethylene oxide, propylene oxide,isopropylene oxide and butylene oxide.

As the silsesquioxane structure-containing structural unit, polyhedraloligomeric silsesquioxane structure-containing structural unit ispreferable. As a monomer which provides a polyhedral oligomericsilsesquioxane structure-containing structural unit, a compound having apolyhedral oligomeric silsesquioxane structure and a polymerizable groupcan be mentioned.

Among the above examples, as the block copolymer, a block copolymercontaining a block of a structural unit having an aromatic group and ablock of a structural unit derived from an (α-substituted) acrylic acidor an (α-substituted) acrylate ester is preferable.

In the case of obtaining a cylinder phase-separated structure orientedin a direction perpendicular to the surface of the substrate, the weightratio of the structural unit having an aromatic group to the structuralunit derived from an (α-substituted) acrylic acid or (α-substituted)acrylate ester is preferably in the range of 60:40 to 90:10, and morepreferably 60:40 to 80:20.

In the case of obtaining a lamellar phase-separated structure orientedin a direction perpendicular to the surface of the substrate, the weightratio of the structural unit having an aromatic group to the structuralunit derived from an (α-substituted) acrylic acid or (α-substituted)acrylate ester is preferably in the range of 35:65 to 60:40, and morepreferably 40:60 to 60:40.

Specific examples of such block copolymers include a block copolymerhaving a block of a structural unit derived from styrene and a block ofa structural unit derived from acrylic acid; a block copolymer having ablock of a structural unit derived from styrene and a block of astructural unit derived from methyl acrylate; a block copolymer having ablock of a structural unit derived from styrene and a block of astructural unit derived from ethyl acrylate; a block copolymer having ablock of a structural unit derived from styrene and a block of astructural unit derived from t-butyl acrylate; a block copolymer havinga block of a structural unit derived from styrene and a block of astructural unit derived from methacrylic acid; a block copolymer havinga block of a structural unit derived from styrene and a block of astructural unit derived from methyl methacrylate; a block copolymerhaving a block of a structural unit derived from styrene and a block ofa structural unit derived from ethyl methacrylate; a block copolymerhaving a block of a structural unit derived from styrene and a block ofa structural unit derived from t-butyl methacrylate; a block copolymerhaving a block of a structural unit containing a polyhedral oligomericsilsesquioxane (POSS) structure and a block of a structural unit derivedfrom acrylic acid; and a block copolymer having a block of a structuralunit containing a polyhedral oligomeric silsesquioxane (POSS) structureand a block of a structural unit derived from methyl acrylate.

In the present embodiment, the use of a block copolymer having a blockof a structural unit derived from styrene (PS) and a block of astructural unit derived from methyl methacrylate (PMMA) is particularlypreferable.

The number average molecular weight (Mn) (the polystyrene equivalentvalue determined by gel permeation chromatography (GPC)) of the blockcopolymer is preferably 6,000 or more, more preferably 8,000 to 200,000,and still more preferably 10,000˜160,000.

The dispersity (Mw/Mn) of the block copolymer is preferably 1.0 to 3.0,more preferably 1.0 to 1.5, and still more preferably 1.0 to 1.3. Here,Mw is the weight average molecular weight.

In the present embodiment, in the resin composition, 1 kind of blockcopolymer may be used, or 2 or more kinds of block copolymers may beused in combination.

In the present embodiment, the amount of the block copolymer in theresin composition may be adjusted depending on the thickness of thelayer containing the block copolymer to be formed.

<Ion Liquid>

In the present embodiment, the resin composition includes a compound(IL) having a cation moiety and a specific anion moiety.

An ion liquid refers to a salt which is present in the form of a liquid.An ion liquid is constituted of a cation moiety and an anion moiety. Theelectrostatic interaction between the cation moiety and the anion moietyis week, and the salt is unlikely to be crystallized. The ion liquid hasa boiling point of 100° C. or lower, and has the followingcharacteristics 1) to 5).

Characteristic 1) The vapor pressure is extremely low. Characteristic 2)Non-flammable over a wide temperature range. Characteristic 3) Maintainsa liquid state over a wide temperature range Characteristic 4) Thedensity can be largely changed. Characteristic 5) The polarity can becontrolled.

As ion liquid, an ion liquid in a liquid state at room temperature, andan ion liquid is a solid state at room temperature may be mentioned.

<<Compound (IL)>>

The compound (IL) is a compound having a cation moiety and an anionmoiety, and the energy of the LUMO of the cation moiety is −4.5 eV ormore, and the energy difference between the LUMO and the HOMO of thecation moiety is 10.0 ev or more, or the Log P value of the anion moietyis 1 to 3. Hereafter, a compound (IL) in which the energy of the LUMO ofthe cation moiety is −4.5 eV or more, and the energy difference betweenthe LUMO and the HOMO of the cation moiety is 10.0 ev or more isreferred to as “compound (IL-ca)”. On the other hand, a compound (IL) inwhich the Log P value of the anion moiety is 1 to 3 is referred to as“compound (IL-an)”.

[Compound (IL-ca)]

Cation Moiety of Compound (IL-ca)

In the cation moiety of the compound (IL-ca), the energy of the LUMO is−4.5 eV or more, and the energy difference between the LUMO and the HOMOis 10.0 ev or more, preferably the energy of the LUMO is −4.5 eV ormore, and the energy difference between the LUMO and the HOMO is 10.5 evor more, and more preferably the energy of the LUMO is −4.3 eV or more,and the energy difference between the LUMO and the HOMO is 10.5 ev ormore.

In the compound (IL-ca), when energy of the LUMO of the cation moietyand the energy difference between the LUMO and the HOMO of the cationmoiety are in the above-mentioned range, the compound (IL) is lesslikely to be decomposed by the annealing treatment in the phaseseparation. As a result, the change rate of the period (L0) of the resincomposition (hereafter, referred to as “L0 change rate”) may be reduced.In general, in order to improve the phase separation performance, it isknown to raise the heating temperature or prolong the heating time inthe annealing treatment during phase separation. When the L0 change rateof the resin composition is small, the annealing margin becomes large,and the phase separation performance is improved.

In the compound (IL), the energy of LUMO of the cation moiety and theenergy difference between LUMO and HOMO of the cation moiety refer tosimulation values by CAChe. For example, the dipole moment of the cationmoiety can be determined by optimization of the structure by CAChe WorkSystem Pro Version 6.1.12.33, using MM geometry (MM2) and PM3 geometry.

Preferable examples of cations in which the energy of LUMO is −4.5 eV ormore and the energy difference in LUMO and HOMO is 10.0 ev or moreinclude a pyrrolidinium ion, a piperidinium ion and an ammonium ion.

That is, preferable examples of the compound (IL-ca) include apyrrolidinium salt, a piperidinium salt and an ammonium salt.

Anion Moiety of Compound (IL-ca)

The anion moiety of the compound (IL-ca) is not particularly limited,and examples thereof include anions represented by any one of generalformulae (a1) to (a5) shown below.

In formula (a1), R represents an aromatic hydrocarbon group which mayhave a substituent, an aliphatic cyclic group which may have asubstituent, or a chain hydrocarbon group which may have a substituent.In formula (a2), R′ represents an alkyl group of 1 to 5 carbon atomsoptionally substituted with a fluorine atom. k represents an integer of1 to 4, and l represents an integer of 0 to 3, provided that k+l=4. informula (a3), R″ represents an alkyl group of 1 to 5 carbon atomsoptionally substituted with a fluorine atom; m represents an integer of1 to 6, and n represents an integer of 0 to 5, provided that m+n=6.

In formula (a4), X″ represents an alkylene group of 2 to 6 carbon atomsin which at least one hydrogen atom has been substituted with a fluorineatom; in formula (a5), Y″ and Z″ each independently represents an alkylgroup of 1 to 10 carbon atoms in which at least one hydrogen atom hasbeen substituted with a fluorine atom;

In general formula (a1), R represents an aromatic hydrocarbon groupwhich may have a substituent, an aliphatic cyclic group which may have asubstituent, or a chain hydrocarbon group which may have a substituent.

In general formula (a1), in the case where R is an aromatic hydrocarbongroup which may have a substituent, examples of the aromatic ringcontained in the aromatic hydrocarbon group include aromatic hydrocarbonrings, such as benzene, biphenyl, fluorene, naphthalene, anthracene andphenanthrene; and aromatic hetero rings in which part of the carbonatoms constituting the aforementioned aromatic hydrocarbon rings hasbeen substituted with a hetero atom. Examples of the hetero atom withinthe aromatic hetero rings include an oxygen atom, a sulfur atom and anitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich 1 hydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group); and a group in which 1 hydrogen atom ofthe aforementioned aryl group has been substituted with an alkylenegroup (an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

As the aromatic hydrocarbon group for R, a phenyl group or a naphthylgroup is preferable, and a phenyl group is more preferable.

In general formula (a1), in the case where R represents an aliphaticcyclic group which may have a substituent, the cyclic group may bealiphatic or aromatic, and may be polycyclic or monocyclic. As themonocyclic aliphatic hydrocarbon group, a group in which 1 hydrogen atomhas been removed from a monocycloalkane is preferable. Themonocycloalkane preferably has 3 to 8 carbon atoms, and specificexamples thereof include cyclopentane, cyclohexane and cyclooctane. Asthe polycyclic group, a group in which 1 hydrogen atom has been removedfrom a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

Among these examples, as the aliphatic cyclic group, groups in which oneor more hydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane or tetracyclododecaneare more preferable.

In general formula (a1), as the chain hydrocarbon group for R, a chainalkyl group is preferable. The chain-like alkyl group preferably has 1to 10 carbon atoms, and specific examples thereof include a linear alkylgroup such as a methyl group, an ethyl group, a propyl group, a butylgroup, a pentyl group, a hexyl group, a heptyl group, an octyl group, anonyl or a decyl group, and a branched alkyl group such as a1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a2-methylpentyl group, a 3-methylpentyl group or a 4-methylpentyl group.

In general formula (a1), examples of the substituent for the aromatichydrocarbon group, the aliphatic cyclic group or the chain hydrocarbongroup for R include a hydroxy group, an alkyl group, a fluorine atom ora fluorinated alkyl group.

In general formula (a1), as R, a methyl group, a trifluoromethyl groupor a p-tolyl group is preferable.

In general formula (a2), R′ represents an alkyl group of 1 to 5 carbonatoms optionally substituted with a fluorine atom.

k represents an integer of 1 to 4, preferably an integer of 3 to 4, andmost preferably 4.

l represents an integer of 0 to 3, preferably 0 to 2, most preferably 0.When 1 is 2 or more, the plurality of R′ may be the same or differentfrom each other, and are preferably the same.

In general formula (a3), R″ represents an alkyl group of 1 to 5 carbonatoms optionally substituted with a fluorine atom;

m represents an integer of 1 to 6, preferably an integer of 3 to 6, andmost preferably 6.

n represents an integer of 0 to 5, preferably 0 to 3, most preferably 0.When n is 2 or more, the plurality of R″ may be the same or differentfrom each other, and are preferably the same.

In formula (a4), X″ represents an alkylene group of 2 to 6 carbon atomsin which at least one hydrogen atom has been substituted with a fluorineatom. The alkylene group may be linear or branched, and has 2 to 6carbon atoms, preferably 3 to 5 carbon atoms, and most preferably 3carbon atoms.

In formula (a5), Y″ and Z″ each independently represents an alkyl groupof 1 to 10 carbon atoms in which at least one hydrogen atom has beensubstituted with a fluorine atom. The alkyl group may be linear orbranched, and has 1 to 10 carbon atoms, preferably 1 to 7 carbon atoms,and most preferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ orthose of the alkyl group for Y″ and Z″ within the above-mentioned rangeof the number of carbon atoms, the more the solubility in an organicsolvent component is improved.

In the alkylene group for X″ and the alkyl group for Y″ and Z″, it ispreferable that the number of hydrogen atoms substituted with fluorineatoms is as large as possible because the acid strength increases Theamount of fluorine atoms within the alkylene group or alkyl group, i.e.,fluorination ratio, is preferably from 70 to 100%, more preferably from90 to 100%, and it is particularly desirable that the alkylene group oralkyl group be a perfluoroalkylene or perfluoroalkyl group in which allhydrogen atoms are substituted with fluorine atoms.

As the anion of the compound (IL-ca), an anion represented by any one ofgeneral formulae (a1), (a2) or (a3) is preferable. From the viewpoint ofsemiconductor production, an anion represented by general formula (a1)is more preferable.

As the compound (IL-ca), a pyrrolidinium salt or a piperidinium salt ispreferable, a pyrrolidinium salt or a piperidinium salt in which theanion moiety has a Log P value of 1 to 3 is more preferable, and apyrrolidinium salt or a piperidinium salt in which the anion moiety hasa Log P value of 1 to 2.5 is still more preferable. The method ofmeasuring the Log P value will be described later.

Specific examples of the compound (IL-ca) are shown below.

With respect to the above compounds (IL-ca-1) to (IL-ca-8), the energy(eV) of LUMO of the cation moiety, the energy difference (eV) betweenLUMO and HOMO of the cation moiety, and the Log P value of the anionmoiety are shown in Table 1 below.

TABLE 1 LUMO of LUMO-HOMO of Compound cation moiety cation moiety LogPvalue of (IL-ca) (eV) (eV) anion moiety (IL-ca-1) −4.17 10.70 3.24(IL-ca-2) −4.19 10.04 3.24 (IL-ca-3) −4.21 10.68 3.24 (IL-ca-4) −4.2110.68 1.12 (IL-ca-5) −4.21 10.68 2.06 (IL-ca-6) −4.06 10.60 −1.13(IL-ca-7) −4.06 10.60 1.12 (IL-ca-8) −4.26 11.47 1.12

Among these examples, as the compound (IL-ca), compound (IL-ca-1) tocompound (IL-ca-5) and compound (IL-ca-8) are preferable, compound(IL-ca-4), (IL-ca-5) or (IL-ca-8) is more preferable, and compound(IL-ca-4) is still more preferable.

[Compound (IL-an)]

Anion Moiety of Compound (IL-an)

The anion moiety of the compound (IL-an) has a Log P value of 1 to 3,preferably a Log P value of 1 to 2.5.

By virtue of the anion moiety of the compound (IL-an) having a Log Pvalue within the above-mentioned range, the interaction between thecompound (IL-an) and the block copolymer is improved, and the phaseseparation performance becomes good.

In the present embodiment, Log P value is a logarithmic value ofn-octanol/water partition coefficient (P), and is an effective parameterfor determining the hydrophilicity/hydrophobicity property of a widevariety of compounds. In general, the partition coefficient isdetermined not through experiments but by calculation. In the presentembodiment, the partition coefficient is determined by optimization ofthe structure by CAChe Work System Pro Version 6.1.12.33, using MMgeometry (MM2) and PM3 geometry.

The larger the Log P value becomes plus 0, it means that thehydrophobicity becomes higher. The larger the absolute value of the logP value becomes minus 0, it means that water solubility becomes higher.The log P value has a negative correlation with water solubility of anorganic compound, and is widely used as a parameter for estimating thehydrophilicity/hydrophobicity of an organic compound.

Examples of anions having a Log P value of 1 to 3 include an anionrepresented by general formula (a1-an) shown below, general formula (a2)shown below or general formula (a3) shown below.

In formula (a1-an), R_(an) represents a fluorinated alkyl group or anaromatic hydrocarbon group. In formula (a2), R′ represents an alkylgroup of 1 to 5 carbon atoms optionally substituted with a fluorineatom. k represents an integer of 1 to 4, and 1 represents an integer of0 to 3, provided that k+l=4. in formula (a3), R″ represents an alkylgroup of 1 to 5 carbon atoms optionally substituted with a fluorineatom; m represents an integer of 1 to 6, and n represents an integer of0 to 5, provided that m+n=6.

In general formula (a1-an), R_(an) represents a fluorinated alkyl groupor an aromatic hydrocarbon group, and is preferably a trifluoromethylgroup or a p-tolyl group.

In general formula (a2), R′, k and l are the same as defined above.

In general formula (a3), R″, m and n are the same as defined above.

As the anion of the compound (IL-an), an anion represented by any one ofgeneral formulae (a1-an), (a2) or (a3) is preferable. From the viewpointof semiconductor production, an anion represented by general formula(a1-an) is more preferable.

[Compound (IL-an)]

Cation Moiety of Compound (IL-an)

The cation moiety of the compound (IL-an) is not particularly limited,and examples thereof include an imidazolium ion, a pyrrolidinium ion, apiperidinium ion and an ammonium ion. Among these salts, in terms ofimproving the phase-separation performance, the cation moiety preferablyhas a substituent. Among these, a cation containing an alkyl groupoptionally having a substituent, or a cation containing a polar group ispreferable. The alkyl group contained in the cation preferably has 1 to12 carbon atoms, more preferably 2 to 6 carbon atoms. Examples of thesubstituent for the alkyl group include a hydroxy group, a vinyl groupand an allyl group. Examples of the polar group contained in the cationinclude a carboxy group, a hydroxy group, an amino group and a sulfogroup.

As the compound (IL-an), an imidazolium salt in which the anion moietyhas a Log P value of 1 to 3 is preferable.

Specific examples of the compound (IL-an) are shown below.

With respect to the compounds (IL-an-1) to (IL-an-6), the Log P value ofthe anion moiety is shown in Table 2 below.

TABLE 2 Ion liquid Compound LogP value of (IL-an) anion moiety (IL-an-1)2.06 (IL-an-2) 2.06 (IL-an-3) 2.06 (IL-an-4) 1.37 (IL-an-5) 1.12(IL-an-6) 1.02

In the present embodiment, as the compound (IL), 1 kind of compound maybe used, or 2 or more kinds of compounds may be used in combination.

In the present embodiment, the amount of the compound (IL) within theresin composition relative to 100 parts by weight of the block copolymeris preferably 0.05 to 50 parts by weight, more preferably 0.1 to 40parts by weight, and still more preferably 0.5 to 30 parts by weight.

When the amount of the compound (IL) is within the above preferablerange, the phase-separation performance may be further improved.

In the resin composition of the present embodiment, the ion liquid maycontain a compound other than the compound (IL) which has a cationmoiety and an anion moiety.

In the ion liquid the amount of the compound (IL) based on the totalweight of the ion liquid is preferably 50% by weight or more, morepreferably 70% by weight or more, still more preferably 90% by weight ormore, and may be even 100% by weight. When the amount of the compound(IL) within the ion liquid is at least as large as the lower limit ofthe above preferable range, the phase-separation performance may befurther improved.

<Organic Solvent Component>

In the present embodiment, the resin composition may be prepared bydissolving the aforementioned block copolymer and the aforementioned ionliquid in an organic solvent component.

The organic solvent component may be any organic solvent which candissolve the respective components to give a uniform solution, and oneor more kinds of any organic solvent can be appropriately selected fromthose which have been conventionally known as solvents for a filmcomposition containing a resin as a main component.

Examples of the organic solvent component include lactones such asγ-butyrolactone; ketones such as acetone, methyl ethyl ketone,cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, and2-heptanone; polyhydric alcohols, such as ethylene glycol, diethyleneglycol, propylene glycol and dipropylene glycol; compounds having anester bond, such as ethylene glycol monoacetate, diethylene glycolmonoacetate, propylene glycol monoacetate, and dipropylene glycolmonoacetate; polyhydric alcohol derivatives including compounds havingan ether bond, such as a monoalkylether (e.g., monomethylether,monoethylether, monopropylether or monobutylether) or monophenylether ofany of these polyhydric alcohols or compounds having an ester bond(among these, propylene glycol monomethyl ether acetate (PGMEA) andpropylene glycol monomethyl ether (PGME) are preferable); cyclic etherssuch as dioxane; esters such as methyl lactate, ethyl lactate (EL),methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethylpyruvate, methyl methoxypropionate, and ethyl ethoxypropionate; andaromatic organic solvents such as anisole, ethylbenzylether,cresylmethylether, diphenylether, dibenzylether, phenetole,butylphenylether, ethylbenzene, diethylbenzene, pentylbenzene,isopropylbenzene, toluene, xylene, cymene and mesitylene.

As the organic solvent component, 1 kind of solvent may be used, or 2 ormore kinds of solvents may be used in combination.

Among these, propylene glycol monomethyl ether acetate (PGMEA),propylene glycol monomethyl ether (PGME), cyclohexanone and ethyllactate (EL) are preferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

For example, when EL is mixed as the polar solvent, the PGMEA:EL weightratio is preferably from 1:9 to 9:1, and more preferably from 2:8 to8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME weight ratio is preferably from 1:9 to 9:1, more preferablyfrom 2:8 to 8:2, and still more preferably 3:7 to 7:3. Alternatively,when PGME and cyclohexanone is mixed as the polar solvent, thePGMEA:(PGME+cyclohexanone) weight ratio is preferably from 1:9 to 9:1,more preferably from 2:8 to 8:2, and still more preferably 3:7 to 7:3.

Further, as the organic solvent component for the resin composition forforming a phase-separated structure, a mixed solvent of γ-butyrolactonewith PGMEA, EL or the aforementioned mixed solvent of PGMEA with a polarsolvent, is also preferable. The mixing ratio (former:latter) of such amixed solvent is preferably from 70:30 to 95:5.

The amount of the organic solvent component in the resin composition forforming a phase-separated structure is not particularly limited, and isadjusted appropriately to a concentration that enables application of acoating solution depending on the thickness of the coating film. Ingeneral, the organic solvent component is used in an amount that yieldsa solid content within a range from 0.2 to 70% by weight, and preferablyfrom 0.2 to 50% by weight.

<Optional Components>

If desired, in addition to the block copolymer, the ion liquid and theorganic solvent component, other miscible additives can also be added tothe resin composition for forming a phase-separated structure. Examplesof such miscible additives include additive resins for improving theperformance of the layer of the brush layer, surfactants for improvingthe applicability, dissolution inhibitors, plasticizers, stabilizers,colorants, halation prevention agents, dyes, sensitizers, baseamplifiers and basic compounds.

The resin composition for forming a phase-separated structure accordingto the present embodiment as described above contains, in addition to ablock copolymer, a compound (IL) having a cation moiety and an anionmoiety, and the energy of the LUMO of the cation moiety is −4.5 eV ormore, and the energy difference between the LUMO and the HOMO of thecation moiety is 10.0 ev or more, or the Log P value of the anion moietyis 1 to 3. Therefore, the phase separation performance is improved.

As described above, In the compound (IL), when energy of the LUMO of thecation moiety and the energy difference between the LUMO and the HOMO ofthe cation moiety are in the above-mentioned range, the compound (IL) isless likely to be decomposed by the annealing treatment in the phaseseparation. As a result, the L0 change rate can be reduced. In general,in order to improve the phase separation performance, it is known toraise the heating temperature or prolong the heating time in theannealing treatment during phase separation. When the L0 change rate ofthe resin composition is small, the annealing margin becomes large, andthe phase separation performance is improved.

Further, as described above, by virtue of the anion moiety of thecompound (IL) having a Log P value within the above-mentioned range, theinteraction between the compound (IL) and the block copolymer isimproved, and the phase separation performance becomes good.

A structure formed by using a resin composition containing the compound(IL) has reduced roughness and is unlikely to have defects generated.

Further, by using a block copolymer having a low polymerization degreein combination with the compound (IL), a structure having a smaller(L0), i.e., a pattern of a finer structure can be formed.

Thus, by using a resin composition for forming a phase-separatedstructure according to the present embodiment, the phase-separationperformance can be further improved.

(Method of Producing Structure Containing Phase-Separated Structure)

A method of producing a structure containing a phase-separated structureaccording to a second aspect of the present invention includes: usingthe resin composition for forming a phase-separated structure accordingto the first aspect to form a layer containing a block copolymer(hereafter, referred to as “step (i)”), and phase-separating the layercontaining the block copolymer (hereafter, referred to as “step (ii)”).

Hereinafter, the method of producing a structure containing aphase-separated structure will be specifically described with referenceto FIG. 1. However, the present invention is not limited to theseembodiments.

FIG. 1 shows an example of one embodiment of the method of forming astructure containing a phase-separated structure.

Firstly, a brush composition is applied to a substrate 1, so as to forma brush layer 2 (FIG. 1 (I)).

Then, to the brush layer 2, the resin composition for forming aphase-separated structure according to the first aspect (resincomposition) is applied, so as to form a layer 3 containing a blockcopolymer (BCP layer 3) (FIG. 1(II); step (i)).

Next, heating is conducted to perform an annealing treatment, so as tophase-separate the BCP layer 3 into a phase 3 a and a phase 3 b (FIG. 1(III); step (ii)).

According to the production method of the present embodiment, that is,the production method including the steps (i) and (ii), a structure 3′containing a phase-separated structure is formed on the substrate 1having the brush layer 2 formed thereon.

[Step (i)]

In step (i), the resin composition for forming a phase-separatedstructure is applied to the substrate 1, so as to form a BCP layer 3.

There are no particular limitations on the type of a substrate, providedthat the resin composition for forming a phase-separated structure canbe coated on the surface of the substrate.

Examples of the substrate include a substrate constituted of aninorganic substance such as a metal (e.g., silicon, copper, chromium,iron or aluminum), glass, titanium oxide, silica or mica; and asubstrate constituted of an organic substance such as an acrylic plate,polystyrene, cellulose, cellulose acetate or phenol resin.

The size and the shape of the substrate is not particularly limited. Thesubstrate does not necessarily need to have a smooth surface, and asubstrate made of various materials and having various shapes can beappropriately selected for use. For example, a multitude of shapes canbe used, such as a substrate having a curved surface, a plate having anuneven surface, and a thin sheet.

On the surface of the substrate, an inorganic and/or organic film may beprovided. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) can be used.

Before forming a BCP layer 3 on the substrate 1, the surface of thesubstrate 1 may be cleaned. By cleaning the surface of the substrate,application of the resin composition for forming a phase-separatedstructure or the brush composition to the substrate 1 may besatisfactorily performed.

As the cleaning treatment, a conventional method may be used, andexamples thereof include an oxygen plasma treatment, a hydrogen plasmatreatment, an ozone oxidation treatment, an acid alkali treatment, and achemical modification treatment. For example, the substrate is immersedin an acidic solution such as a sulfuric acid/hydrogen peroxide aqueoussolution, followed by washing with water and drying. Thereafter, a BCPlayer 3 or a brush layer 2 is formed on the surface of the substrate.

Before forming a BCP layer 3 on the substrate 1, the surface of thesubstrate 1 may be cleaned.

A neutralization treatment is a treatment in which the surface of thesubstrate is modified so as to have affinity for all polymersconstituting the block copolymer. By the neutralization treatment, itbecomes possible to prevent only phases of specific polymers to comeinto contact with the surface of the substrate by phase separation. Forexample, prior to forming a BCP layer 3, on the surface of the substrate1, it is preferable to form a brush layer 2 depending on the kind ofblock copolymer to be used. As a result, by phase-separation of the BCPlayer 3, a cylinder structure or lamellar structure oriented in adirection perpendicular to the surface of the substrate 1 can bereliably formed.

Specifically, on the surface of the substrate 1, a brush layer 2 isformed using a brush composition having affinity for all polymersconstituting the block copolymer.

The brush composition can be appropriately selected from conventionalresin compositions used for forming a thin film, depending on the kindof polymers constituting the block copolymer.

Examples of the brush composition include a composition containing aresin which has all structural units of the polymers constituting theblock copolymer, and a composition containing a resin which has allstructural units having high affinity for the polymers constituting theblock copolymer.

For example, when a PS-PMMA block copolymer is used, as the brushcomposition, it is preferable to use a resin composition containing bothPS and PMMA as blocks, or a compound or a composition containing both aportion having a high affinity for an aromatic ring and a portion havinga high affinity for a functional group with high polarity.

Examples of the resin composition containing both PS and PMMA as blocksinclude a random copolymer of PS and PMMA, and an alternating polymer ofPS and PMMA (a copolymer in which the respective monomers arealternately copolymerized).

Examples of the composition containing both a portion having a highaffinity for PS and a portion having a high affinity for PMMA include aresin composition obtained by polymerizing at least a monomer having anaromatic ring and a monomer having a substituent with high polarity.Examples of the monomer having an aromatic ring include a monomer havinga group in which one hydrogen atom has been removed from the ring of anaromatic hydrocarbon, such as a phenyl group, a biphenyl group, afluorenyl group, a naphthyl group, an anthryl group or a phenanthrylgroup, or a monomer having a hetero aryl group such as theaforementioned group in which part of the carbon atoms constituting thering of the group has been substituted with a hetero atom such as anoxygen atom, a sulfur atom or a nitrogen atom. Examples of the monomerhaving a substituent with high polarity include a monomer having atrimethoxysilyl group, a trichlorosilyl group, a carboxy group, ahydroxy group, a cyano group or a hydroxyalkyl group in which part ofthe hydrogen atoms of the alkyl group has been substituted with fluorineatoms.

Examples of the compound containing both a portion having a highaffinity for PS and a portion having a high affinity for PMMA include acompound having both an aryl group such as a phenethyltrichlorosilaneand a substituent with high polarity, and a compound having both analkyl group and a substituent with high polarity, such as an alkylsilanecompound.

Further, as the brush composition, for example, a heat-polymerizableresin composition, or a photosensitive resin composition such as apositive resist composition or a negative resist composition can also bementioned.

The brush layer may be formed by a conventional method.

The method of applying the brush composition to the substrate 1 to forma brush layer 2 is not particularly limited, and the brush layer 2 canbe formed by a conventional method.

For example, the brush composition can be applied to the substrate 1 bya conventional method using a spinner or the like to form a coating filmon the substrate 1, followed by drying, thereby forming a brush layer 2.

The drying method of the coating film is not particularly limited,provided it can volatilize the solvent contained in the brushcomposition, and a baking method and the like are exemplified. Thebaking temperature is preferably 80° C. to 300° C., more preferably 180°C. to 270° C., and still more preferably 220° C. to 250° C. The bakingtime is preferably 30 seconds to 500 seconds, and more preferably 60seconds to 400 seconds.

The thickness of the brush layer 2 after drying of the coating film ispreferably about 10 to 100 nm, and more preferably about 40 to 90 nm.

Subsequently, on the brush layer 2, a layer 3 containing a blockcopolymer having a plurality of blocks bonded (BCP layer 3) is formed.

The method of forming the BCP layer 3 on the brush layer 2 is notparticularly limited, and examples thereof include a method in which theresin composition is applied to the brush layer 2 by a conventionalmethod using spincoating or a spinner, followed by drying.

The drying method of the coating film of the resin composition is notparticularly limited, provided it can volatilize the organic solventcomponent included in the resin composition, and a baking method or thelike can be mentioned. At this time, prior to the phase-separationoperation in step (ii), it is preferable to conduct the baking or thelike in a manner such that the ion liquid remains in the coating film asmuch as possible. Therefore, the baking is temperature is, for example,preferably from 60 to 350° C., and more preferably from 80 to 280° C.The baking time is, for example, preferably from 10 to 3,000 seconds,and more preferably from 20 to 120 seconds.

The BCP layer 3 may have a thickness satisfactory for phase-separationto occur. In consideration of the kind of the substrate 1, the structureperiod size of the phase-separated structure to be formed, and theuniformity of the nanostructure, the thickness is preferably 20 to 100nm, and more preferably 30 to 80 nm.

For example, in the case where the substrate 1 is an Si substrate or anSiO₂, the thickness of the BCP layer 3 is preferably 20 to 100 nm, andmore preferably 30 to 80 nm.

In the case where the substrate 1 is a Cu substrate, the thickness ofthe BCP layer 3 is preferably 10 to 100 nm, and more preferably 30 to 80nm.

[Step (ii)]

Step (ii), the layer 3 containing a block copolymer formed on thesubstrate 1 is phase-separated.

By heating the substrate 1 after step (i) to conduct the annealtreatment, the block copolymer is selectively removed, such that aphase-separated structure in which at least part of the surface of thesubstrate 1 is exposed is formed. That is, on the substrate 1, astructure 3′ containing a phase-separated structure in which phase 3 aand phase 3 b are phase separated is produced.

The anneal treatment is preferably conducted at a temperature at leastas high as the glass transition temperature of the block copolymer usedand lower than the heat decomposition temperature. For example, in thecase where the block copolymer is a polystyrene-polymethacrylate(PS-PMMA) block copolymer, (number average molecular weight: 6000 to200,000), the heat treatment is preferably conducted at 100 to 400° C.,more preferably 120 to 350° C., and most preferably 150 to 300° C. Theheating time is preferably 30 to 3,600 seconds, and more preferably 120to 600 seconds.

Further, the anneal treatment is preferably conducted in a low reactivegas such as nitrogen.

By the method of producing a structure containing a phase-separatedstructure according to the present embodiment described heretofore, thephase-separation performance of the block copolymer can be enhanced, anda fine structure with a good shape can be formed, as compared toconventional lithography techniques.

In addition, on the surface of the substrate, a substrate provided witha nanostructure which has the position and the orientation designed morefreely can be produced. For example, the formed structure has highadhesion to the substrate, and is likely to have a phase-separatedstructure with a cylinder structure or lamellar structure oriented in adirection perpendicular to the surface of the substrate.

[Optional Step]

The method of forming a structure containing a phase-separated structureaccording to the second aspect of the present invention is not limitedto the above embodiment, and may include a step (optional step) otherthan steps (i) and (ii).

Examples of the optional steps include a step of selectively removing aphase constituted of at least one block of the plurality of blocksconstituting the block copolymer contained in the BCP layer 3(hereafter, referred to as “step (iii)”), and a guide pattern formationstep.

Step (iii)

In step (iii), from the BCP layer 3 formed on the brush layer 2, a phaseconstituted of at least one block of the plurality of blocksconstituting the block copolymer (phase 3 a and phase 3 b) isselectively removed. In this manner, a fine pattern (polymericnanostructure) can be formed.

Examples of the method of selectively removing a phase constituted of ablock include a method in which an oxygen plasma treatment or a hydrogenplasma treatment is conducted on the BCP layer.

Hereafter, among the blocks constituting the block copolymer, a blockwhich is not selectively removed is referred to as “block P_(A)”, and ablock to be selectively removed is referred to as “block P_(B)”. Forexample, after the phase separation of a layer containing a PS-PMMAblock copolymer, by subjecting the layer to an oxygen plasma treatmentor a hydrogen plasma treatment, the phase of PM MA is selectivelyremoved. In such a case, the PS portion is the block P_(A), and the PMMAportion is the block P_(B).

FIG. 2 shows an example of one embodiment of step (iii).

In the embodiment shown in FIG. 2, by conducting oxygen plasma treatmenton the structure 3′ produced on the substrate 1 in step (ii), the phase3 a is selectively removed, and a pattern (polymeric nanostructure)constituted of phases 3 b separated from each other is formed. In thiscase, the phase 3 b is the phase constituted of the block P_(A), and thephase 3 a is the phase constituted of the block P_(B).

The substrate 1 having a pattern formed by phase-separation of the BCPlayer 3 as described above may be used as it is, or may be furtherheated to modify the shape of the pattern (polymeric nanostructure) onthe substrate 1.

The heat treatment is preferably conducted at a temperature at least ashigh as the glass transition temperature of the block copolymer used andlower than the heat decomposition temperature. Further, the heating ispreferably conducted in a low reactive gas such as nitrogen.

Guide Pattern Forming Step

In the method of forming a structure containing a phase-separatedstructure according to the second aspect of the present invention, astep of forming a guide pattern on the brush layer (guide patternforming step) may be included. In this manner, it becomes possible tocontrol the arrangement of the phase-separated structure.

For example, in the case of a block copolymer where a randomfingerprint-patterned phase separation structure is formed without usinga guide pattern, by providing a trench pattern of a resist film on thesurface of the brush layer, a phase separation structure arranged alongthe trench can be obtained. The guide pattern can be provided on thebrush layer 2 in accordance with the above-described principle. Further,when the surface of the guide pattern has affinity for any of thepolymers constituting the block copolymer, a phase separation structurehaving a cylinder structure or lamellar structure arranged in theperpendicular direction of the surface of the substrate can be morereliably formed.

The guide pattern can be formed, for example, using a resistcomposition.

The resist composition for forming the guide pattern can beappropriately selected from resist compositions or a modified productthereof typically used for forming a resist pattern which have affinityfor any of the polymers constituting the block copolymer. The resistcomposition may be either a positive resist composition capable offorming a positive pattern in which exposed portions of the resist filmare dissolved and removed, or a negative resist pattern capable offorming a negative pattern in which unexposed portions of the resistfilm are dissolved and removed, but a negative resist composition ispreferable. As the negative resist composition, for example, a resistcomposition containing an acid-generator component and a base componentwhich exhibits decreased solubility in an organic solvent-containingdeveloping solution under action of acid, wherein the base componentcontains a resin component having a structural unit which is decomposedby action of acid to exhibit increased polarity, is preferable.

When the resin composition is cast onto the brush layer having the guidepattern formed thereon, an anneal treatment is conducted to causephase-separation. Therefore, the resist pattern for forming a guidepattern is preferably capable of forming a resist film which exhibitssolvent resistance and heat resistance.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

Examples 1 to 14, Comparative Examples 1 to 3

<Preparation of Resin Composition>

The components shown in Table 3 were mixed together and dissolved toobtain each resin composition (solid content: 0.7 wt %). Ion liquidswere blended in equimolar amounts.

TABLE 3 Resin Block Organic solvent composition copolymer Ion liquidcomponent Example 1 BCP-1 (IL-ca-1) (S)-1 [100] [5.59] [12400] Example 2BCP-1 (IL-ca-2) (S)-1 [100] [5.80] [12400] Example 3 BCP-1 (IL-ca-3)(S)-1 [100] [5.41] [12400] Example 4 BCP-1 (IL-ca-4) (S)-1 [100] [3.73][12400] Example 5 BCP-1 (IL-ca-5) (S)-1 [100] [3.68] [12400] Example 6BCP-1 (IL-ca-6) (S)-1 [100] [4.32] [12400] Example 7 BCP-1 (IL-ca-7)(S)-1 [100] [5.01] [12400] Example 8 BCP-1 (IL-ca-8) (S)-1 [100] [3.37][12400] Comparative BCP-1 (IL-A) (S)-1 Example 1 [100] [5.73] [12400]Example 9 BCP-1 (IL-an-1) (S)-1 [100] [4.00] [12400] Example 10 BCP-1(IL-an-2) (S)-1 [100] [3.64] [12400] Example 11 BCP-1 (IL-an-3) (S)-1[100] [3.28] [12400] Example 12 BCP-1 (IL-an-4) (S)-1 [100] [2.54][12400] Example 13 BCP-1 (IL-an-5) (S)-1 [100] [3.33] [12400] Example 14BCP-1 (IL-an-6) (S)-1 [100] [3.62] [12400] Comparative BCP-1 (IL-B)(S)-1 Example 2 [100] [5.01] [12400] Comparative BCP-1 (IL-C) (S)-1Example 3 [100] [2.64] [12400]

In Table 3, the reference characters indicate the following. The valuesin brackets [ ] indicate the amount (in terms of parts by weight) of thecomponent added.

BCP-1: a block copolymer of polystyrene (PS block) and poly(methylmethacrylate) (PMMA block) [Mn: PS 23,000, PMMA 23,000, total 46000;PS/PMMA compositional ratio (weight ratio) 50.0/50.0; dispersity 1.02].

(S)-1: a mixed solvent of propylene glycol monomethyl ether acetate(PGMEA)/propylene glycol monomethyl ether (PGME)=6/4 (weight ratio)

(IL-ca-1) to (IL-ca-8): compounds represented by the following chemicalformulae (IL-ca-1) to (IL-ca-8), respectively

(IL-A): compound represented by the following chemical formula (IL-A)

(IL-an-1) to (IL-an-6): compounds represented by the following chemicalformulae (IL-an-1) to (IL-an-6), respectively

(IL-B): compound represented by the following chemical formula (IL-B)

(IL-C): compound represented by the following chemical formula (IL-C)

With respect to each ion liquid, the energy of LUMO of the cationmoiety, the energy difference between LUMO and HOMO of the cationmoiety, and the Log P value of the anion moiety are shown in Table 2.The energy of LUMO of the cation moiety, the energy difference betweenLUMO and HOMO of the cation moiety, and the Log P value are valuesdetermined by optimization of the structure by CAChe Work System ProVersion 6.1.12.33, using MM geometry (MM2) and PM3 geometry.

<Evaluation of Film Retention Ratio>

Each resin composition shown in Table 3 was adjusted to a solid contentof 0.7% by weight and applied to a wafer, and baking was conducted underthe following conditions to form a coating film.

Condition a) Baking in air at 90° C. for 1 minute.

Condition b) Baking in air at 230° C. for 15 minutes.

The film thickness of the coating film formed under each condition wasmeasured, and the film retention ratio was calculated by the followingformula.Film retention ratio (%)=[(Film thickness of coating film formed undercondition b))/(Film thickness of coating film formed under conditiona))]×100

The results are shown in Table 4.

(Production of Structure Containing Phase-Separated Structure)

[Step (i)]

The following brush composition was applied to a 300 mm silicon (Si)wafer by spin-coating (number of rotation: 1,500 rpm, 60 seconds),followed by drying by baking in air at 250° C. for 60 seconds, so as toform a brush layer having a film thickness of 100 nm.

As the brush composition, a PGMEA solution of a copolymer having astyrene (St) unit and a methyl methacrylate (MMA) unit (resinconcentration: 3.3 wt %) was used.

Subsequently, the brush layer was rinsed with OK73 thinner (productname; manufactured by Tokyo Ohka Kogyo Co., Ltd.), so as to remove theuncrosslinked portions and the like of the random copolymer. Then,baking was conducted at 250° C. for 60 seconds. After the baking, thebrush layer formed on the Si wafer had a film thickness of 2 nm.

Thereafter, each resin composition was spin-coated (number of rotation:1,500 rpm, 60 seconds) to cover the brush layer formed on the wafer, soas to form a PS-PMMA block copolymer layer having a film thickness of 30nm.

[Step (ii)]

Next, an anneal treatment was conducted under the following condition 1)or 2), so as to phase-separate the PS-PMMA block copolymer layer into aphase constituted of PS and a phase constituted of PMMA, thereby forminga phase-separated structure.

Condition 1) Heating at 200° C. for 60 seconds.

Condition 2) Heating at 200° C. for 30 minutes.

After steps (i) and (ii), a structure containing a phase-separatedstructure was formed on the brush layer in the case of using the resincompositions of each example.

[Step (iii)]

A wet etching treatment was conducted on the silicon (Si) wafer havingthe phase-separated structure formed thereon, so as to selectivelyremove the phase constituted of PMMA.

<Evaluation of Change Rate in Period>

In step (ii) in the aforementioned <Production of structure containingphase-separated structure>, the period (L0 1 min) of the phase-separatedstructure formed by annealing treatment under condition 1), and theperiod (L0 30 min) of the phase-separated structure formed by annealingtreatment under condition 2) were determined. The period of thephase-separated structure was measured by a method using an imageanalysis software MATLAB.

From the following formula, the change rate in the period (L0 changerate) was determined.L0 change rate (%)={|[(L0 1 min)−(L0 30 min)|]/(L0 1 min)}×100

The results are shown in Table 4.

TABLE 4 Ion liquid LUMO - LUMO of HOMO of LogP Film L0 cation cationvalue of retention L0 L0 change moiety moiety anion ratio 1 min 30 minrate Compound (eV) (eV) moiety (%) (nm) (nm) (%) Example 1 −4.17 10.703.24 88.48 29.5 28.5 3.39 Example 2 −4.19 10.04 3.24 84.43 29.6 28.24.73 Example 3 −4.21 10.68 3.24 86.06 29.5 28.4 3.73 Example 4 −4.2110.68 1.12 95.99 27.6 26.9 2.5 Example 5 −4.21 10.68 2.06 96.71 28.528.0 1.75 Example 6 −4.06 10.60 −1.13 — 27.3 25.8 5.49 Example 7 −4.0610.60 1.12 80.25 28.5 27.0 5.26 Example 8 −4.26 11.47 1.12 97.50 27.526.8 2.55 Comparative −4.93 8.69 3.24 77.18 29.0 25.8 11.03 Example 1Example 9 −4.93 8.69 2.06 94.49 28.7 27.9 2.79 Example 10 −4.94 9.662.06 — 28.4 27.7 2.46 Example 11 −4.95 10.00 2.06 96.18 28.5 27.6 3.16Example 12 −4.95 10.00 1.37 — 26.0 25.3 2.69 Example 13 −4.95 10.00 1.1287.88 27.3 25.9 4.95 Example 14 −4.95 10.00 1.02 92.95 — — — Comparative−4.95 10.00 3.24 84.52 29.1 25.9 11.00 Example 2 Comparative −4.95 10.00−1.13 73.37 — — — Example 3

From the results shown in Table 4, it was confirmed that the resincompositions of Examples 1 to 14 exhibited excellent phase-separationperformance.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A resin composition for forming a phase-separatedstructure, comprising: a block copolymer; and a non-polymeric ion liquidcontaining a compound (IL) having a cation moiety and an anion moiety,wherein the amount of the compound (IL) within the resin compositionrelative to 100 parts by weight of the block copolymer is 0.05 to 50parts by weight, and wherein the LUMO of the cation moiety is −4.5 eV ormore, and the difference between the LUMO and the HOMO of the cationmoiety is 10.0 ev or more, and/or the Log P of the anion moiety is 1 to3.
 2. The resin composition for forming a phase-separated structureaccording to claim 1, wherein the LUMO of the cation moiety is −4.5 eVor more, and the difference between the LUMO and the HOMO of the cationmoiety is 10.5 ev or more, or the Log P of the anion moiety is 1 to 3.3. The resin composition for forming a phase-separated structureaccording to claim 1, wherein the compound (IL) is a pyrrolidinium salt,a piperidinium salt or an ammonium salt.
 4. The resin composition forforming a phase-separated structure according to claim 1, wherein thecompound (IL) is a pyrrolidinium salt or a piperidinium salt.
 5. Theresin composition for forming a phase-separated structure according toclaim 4, wherein the Log P of the anion moiety is 1 to
 3. 6. The resincomposition for forming a phase-separated structure according to claim1, wherein the compound (IL) is an imidazolium salt, and the Log P ofthe anion moiety is 1 to
 3. 7. A method of producing a structurecontaining a phase-separated structure, comprising: using the resincomposition for forming a phase-separated structure according to claim 1to form a layer containing a block copolymer, and phase-separating thelayer containing the block copolymer.